#include "blaswrap.h"
#include "f2c.h"

/* Subroutine */ int ztgexc_(logical *wantq, logical *wantz, integer *n, 
	doublecomplex *a, integer *lda, doublecomplex *b, integer *ldb, 
	doublecomplex *q, integer *ldq, doublecomplex *z__, integer *ldz, 
	integer *ifst, integer *ilst, integer *info)
{
/*  -- LAPACK routine (version 3.0) --   
       Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
       Courant Institute, Argonne National Lab, and Rice University   
       June 30, 1999   


    Purpose   
    =======   

    ZTGEXC reorders the generalized Schur decomposition of a complex   
    matrix pair (A,B), using an unitary equivalence transformation   
    (A, B) := Q * (A, B) * Z', so that the diagonal block of (A, B) with   
    row index IFST is moved to row ILST.   

    (A, B) must be in generalized Schur canonical form, that is, A and   
    B are both upper triangular.   

    Optionally, the matrices Q and Z of generalized Schur vectors are   
    updated.   

           Q(in) * A(in) * Z(in)' = Q(out) * A(out) * Z(out)'   
           Q(in) * B(in) * Z(in)' = Q(out) * B(out) * Z(out)'   

    Arguments   
    =========   

    WANTQ   (input) LOGICAL   
            .TRUE. : update the left transformation matrix Q;   
            .FALSE.: do not update Q.   

    WANTZ   (input) LOGICAL   
            .TRUE. : update the right transformation matrix Z;   
            .FALSE.: do not update Z.   

    N       (input) INTEGER   
            The order of the matrices A and B. N >= 0.   

    A       (input/output) COMPLEX*16 array, dimension (LDA,N)   
            On entry, the upper triangular matrix A in the pair (A, B).   
            On exit, the updated matrix A.   

    LDA     (input)  INTEGER   
            The leading dimension of the array A. LDA >= max(1,N).   

    B       (input/output) COMPLEX*16 array, dimension (LDB,N)   
            On entry, the upper triangular matrix B in the pair (A, B).   
            On exit, the updated matrix B.   

    LDB     (input)  INTEGER   
            The leading dimension of the array B. LDB >= max(1,N).   

    Q       (input/output) COMPLEX*16 array, dimension (LDZ,N)   
            On entry, if WANTQ = .TRUE., the unitary matrix Q.   
            On exit, the updated matrix Q.   
            If WANTQ = .FALSE., Q is not referenced.   

    LDQ     (input) INTEGER   
            The leading dimension of the array Q. LDQ >= 1;   
            If WANTQ = .TRUE., LDQ >= N.   

    Z       (input/output) COMPLEX*16 array, dimension (LDZ,N)   
            On entry, if WANTZ = .TRUE., the unitary matrix Z.   
            On exit, the updated matrix Z.   
            If WANTZ = .FALSE., Z is not referenced.   

    LDZ     (input) INTEGER   
            The leading dimension of the array Z. LDZ >= 1;   
            If WANTZ = .TRUE., LDZ >= N.   

    IFST    (input/output) INTEGER   
    ILST    (input/output) INTEGER   
            Specify the reordering of the diagonal blocks of (A, B).   
            The block with row index IFST is moved to row ILST, by a   
            sequence of swapping between adjacent blocks.   

    INFO    (output) INTEGER   
             =0:  Successful exit.   
             <0:  if INFO = -i, the i-th argument had an illegal value.   
             =1:  The transformed matrix pair (A, B) would be too far   
                  from generalized Schur form; the problem is ill-   
                  conditioned. (A, B) may have been partially reordered,   
                  and ILST points to the first row of the current   
                  position of the block being moved.   


    Further Details   
    ===============   

    Based on contributions by   
       Bo Kagstrom and Peter Poromaa, Department of Computing Science,   
       Umea University, S-901 87 Umea, Sweden.   

    [1] B. Kagstrom; A Direct Method for Reordering Eigenvalues in the   
        Generalized Real Schur Form of a Regular Matrix Pair (A, B), in   
        M.S. Moonen et al (eds), Linear Algebra for Large Scale and   
        Real-Time Applications, Kluwer Academic Publ. 1993, pp 195-218.   

    [2] B. Kagstrom and P. Poromaa; Computing Eigenspaces with Specified   
        Eigenvalues of a Regular Matrix Pair (A, B) and Condition   
        Estimation: Theory, Algorithms and Software, Report   
        UMINF - 94.04, Department of Computing Science, Umea University,   
        S-901 87 Umea, Sweden, 1994. Also as LAPACK Working Note 87.   
        To appear in Numerical Algorithms, 1996.   

    [3] B. Kagstrom and P. Poromaa, LAPACK-Style Algorithms and Software   
        for Solving the Generalized Sylvester Equation and Estimating the   
        Separation between Regular Matrix Pairs, Report UMINF - 93.23,   
        Department of Computing Science, Umea University, S-901 87 Umea,   
        Sweden, December 1993, Revised April 1994, Also as LAPACK working   
        Note 75. To appear in ACM Trans. on Math. Software, Vol 22, No 1,   
        1996.   

    =====================================================================   


       Decode and test input arguments.   
       Parameter adjustments */
    /* System generated locals */
    integer a_dim1, a_offset, b_dim1, b_offset, q_dim1, q_offset, z_dim1, 
	    z_offset, i__1;
    /* Local variables */
    static integer here;
    extern /* Subroutine */ int ztgex2_(logical *, logical *, integer *, 
	    doublecomplex *, integer *, doublecomplex *, integer *, 
	    doublecomplex *, integer *, doublecomplex *, integer *, integer *,
	     integer *), xerbla_(char *, integer *);

    a_dim1 = *lda;
    a_offset = 1 + a_dim1 * 1;
    a -= a_offset;
    b_dim1 = *ldb;
    b_offset = 1 + b_dim1 * 1;
    b -= b_offset;
    q_dim1 = *ldq;
    q_offset = 1 + q_dim1 * 1;
    q -= q_offset;
    z_dim1 = *ldz;
    z_offset = 1 + z_dim1 * 1;
    z__ -= z_offset;

    /* Function Body */
    *info = 0;
    if (*n < 0) {
	*info = -3;
    } else if (*lda < max(1,*n)) {
	*info = -5;
    } else if (*ldb < max(1,*n)) {
	*info = -7;
    } else if (*ldq < 1 || *wantq && *ldq < max(1,*n)) {
	*info = -9;
    } else if (*ldz < 1 || *wantz && *ldz < max(1,*n)) {
	*info = -11;
    } else if (*ifst < 1 || *ifst > *n) {
	*info = -12;
    } else if (*ilst < 1 || *ilst > *n) {
	*info = -13;
    }
    if (*info != 0) {
	i__1 = -(*info);
	xerbla_("ZTGEXC", &i__1);
	return 0;
    }

/*     Quick return if possible */

    if (*n <= 1) {
	return 0;
    }
    if (*ifst == *ilst) {
	return 0;
    }

    if (*ifst < *ilst) {

	here = *ifst;

L10:

/*        Swap with next one below */

	ztgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], ldb, &q[
		q_offset], ldq, &z__[z_offset], ldz, &here, info);
	if (*info != 0) {
	    *ilst = here;
	    return 0;
	}
	++here;
	if (here < *ilst) {
	    goto L10;
	}
	--here;
    } else {
	here = *ifst - 1;

L20:

/*        Swap with next one above */

	ztgex2_(wantq, wantz, n, &a[a_offset], lda, &b[b_offset], ldb, &q[
		q_offset], ldq, &z__[z_offset], ldz, &here, info);
	if (*info != 0) {
	    *ilst = here;
	    return 0;
	}
	--here;
	if (here >= *ilst) {
	    goto L20;
	}
	++here;
    }
    *ilst = here;
    return 0;

/*     End of ZTGEXC */

} /* ztgexc_ */

